Production of sebacic acid



United States Patent PRODUCTION OF SEBACIC ACID Werner Stein,Dusseldorf-Holthausen, Germany, assignor to Henkel & Cie., G. m. b. H.,Dusseldorf-Holthausen, Germany, a corporation of Germany No Drawing.Application July 8, 1952,

Serial No. 297,760

Claims priority, application Germany July 11, 1951 7 Claims.(Cl.260--537) In the conventional methods for the production of sebacicacid by oxidative cleavage of castor oil with caustic alkalis atincreased temperatures, the resulting 'ICECiiOIl product constitutes arelatively heavily viscous mass by reason of the high melting points ofthe alkali salts of sebacic acid. For this reason the working up of thereaction products presents certain difficulties that are not too easilyovercome.

One object of the invention comprises the elimination of theaforementioned difiiculties and at the same time the obtaining of a moreefficient reaction of the initial reaction components. This and furtherobjects of the invention will be apparent from the followingdescription.

In accordance with the invention, alkali soaps of fatty acids which aresubstantially liquid at the temperature of reaction are added to theinitial reaction mix to be treated for the production of sebacic acidsalts.

Castor oil or the therefrom obtained ricinoleic acid constitutes at themoment the raw material of largest practical significance for theobtaining of sebacic acid or acid salt. If castor oil is used as theimmediate starting material, it is necessary to add to the initialreaction mix the water which will be consumed during the reaction. Suchwater is automatically produced when using ricinoleic acid by reason ofthe neutralization thereof with caustic alkali. Where reference istherefore made hereinto proceeding in the absence of water or thesubstantial absence thereof there is to be understood in accordance withthe foregoing the use of the aforementioned minimum amount of water.

Caustic alkalis useful in the practice of the process are principallycaustic soda and in many cases also caustic potash.

For the purpose of reducing the consistency of the reaction mixprimarily additions of the alkali salts of the soap forming straight orbranched chained, natural or synthetic fatty acids may be used withinthe scope of the invention. The fatty acids to be used may contain atleast 8 carbon atoms in their molecule. The melting points of fattyacids or fatty acid mixtures, as they are I preferably used in theprocess of this invention do. not change very much with the increasingchain length of the fatty acids. Therefore, the upper limit of chainlength depends only by the chain length of the available acids. Wool waxand montan wax contain fatty acids with 25-30 carbon atoms in theirmolecule. Such high fatty acids may also be produced in synthetic way e.g. by the catalytic reaction between carbon oxyde and hydrogen andolefins, known oxo process, and by subsequent conversion of the alcoholsor aldehydes into fatty acids.

It is sometimes desirable and may be of advantage to produce the soapswithin the course of the sebacic acid production such as by alkalioxidation of corresponding alcohols. If unsaturated fatty acids free ofoxy groups are added to the initial reaction mix, it is also possible toobtain with such additions the results in accordance with the inventionby reasonof the decomposition of these fatty acids into suitableproducts by the action of alkali as part of the reaction leading tosebacic acid or acid salts. inasmuch as these reactions, such as thealkali oxidation of alcohols, and the decomposition ofunsaturated'fa'tty acids proceeds with consumption of alkali,

it is necessary to take this into account when calculating the alkalirequirements of the initial reaction components .for the'productiqupfsebacicacid or acid salts.

2,696,500 Patented Dec. 7, 1954 The amount of alkali soaps to be addedmay be at least one half of the alkali soap of the ricinoleic acid. Theamount may be increased and if the production of sebacic acid iscombined with the alkali decomposition of unsaturated fatty acids intosoaps of saturated fatty acids of lower chain length, or with the alkalioxidation of fatty alcohols to salts of the fatty acids, the amount ofadded soap may be increased to four times the amount of ricinoleic acidsoap.

The formation of sebacic acid proceeds already at temperatures ofapproximately 200 C. plus or minus; for the practical, large scaleoperation of the process preferred temperatures of above about 235 C.are recommended which may be increased to above about 350 C. up to thetemperature at which appreciable decomposition of reactants or reactionproducts would occur which temperature may be modified or influenced toreduce decomposition or the danger thereof by the addition of, forinstance water. The maximum amount of water may be limited so that itforms a 50% by weight alkali lye with the caustic alkali, added to thestarting materials. This limitation is given only by economical reasons.The reaction is possible even with greater amounts of water. Under suchcircumstances it is necessary to observe every necessary precaution whenblowing off the hydrogen produced during the reaction which is carriedout either continuously or in batch portions during the reaction or onlyafter the completion of the reaction, so as to avoid a sudden pressuredrop and resultant boiling and foaming of the reactant which in turn mayentail losses of materials and the clogging of reaction apparatuses.Such boiling of the reaction mix may be avoided by maintaining in theapparatus a pressure above the saturation pressure of the water. This isthe only reason, why the maintaining of a certain pressure in thereaction vessel is commendable. Its amount depends on the amount ofwater, the amount ofhydrogen, formed during the reaction and thecontents of the reaction vessel. The reaction itself does not depend onthe pressure.

It has been further discovered within the scope of the invention and asan embodiment thereof that the speed of reaction may be increased byeffecting the reaction in the presence of cadmium or cadmium additions.In a certain case, when a heating of two hours were necessary to obtaina formation of sebacic acid 84% of theory at 275 C. without presence ofcadmium, the addition of 5% cadmium oxide, calculated upon the amount ofricinoleic acid, increased the velocity of reaction in such a manner,that the 84% of sebacic acid had already formed, when the vessel wasopened after a reaction time of one hour. The cadmium which may be addedto the initial reaction components in any desired form whethersubstantially free or chemically bound, would eventually become deposited in the form of a cadmium. layer on the walls of the autoclave.These little amounts of cadmium are sufficient to catalyze the reaction,so that in later runs the special addition of cadmium may becomeunnecessary. It is alternatively possible to use autoclaves initiallyprovidedwith a cadmium lining.

Upon completion of the reaction, the reaction mix, if necessary, isdissolved in or diluted with water whereafter the monobasic fatty acidsare separated from the sebacic acid, preferably by fractionatedprecipitation with acids which constitutes a relatively simple recoveryprocedure. If the solution of sebacic salt, remaining after theprecipitation of the first separated monobasic acids, is acidified whilehot there is obtained upon cooling a crystallizate which is particularlywell filterable.

The separation of the sebacic acid or sebacic acid salts from themonocarbonic acids present in the reaction product may be, howevereffected also in different manner such as by solvent extraction ortreatment with organic solvents for the monocarbonic acids.

The addition of alkali soaps to the reaction mixture in accordance withthe invention effects a liquification or thinning of this mixture andbeneficially influences the efficiency of the reaction itself, as wellas the workability of the reaction product. The substantially liquidinitial reaction mixpe'rmits a thorough mixture of reaction componentsandassures a far reaching thorough substantially complete reaction ofthe materials. Furthermore, the

initial reaction mix and the reaction products in various stages ofcompleteness of reaction possess a materially superior flowability ascompared with reaction mixes only composed of castor oil or ricinoleicacid and caustic alkali. The invention makes it thus :possible for theLfirst time to operate in a relatively simple, substantially continuousmannenusing duct systems-or similar apparatuses for thesubstantiallycontinuous transportuof reaction componentinto and through a reactionzone ifor the substantially continuous production :of sebaci'c .acid orisebacic acid salts.

A still further liquification or reduction in consistency of materialsmay be obtained by .th'esaddition of Water which, however, in thepresence of the fatty facidlsoap addition in accordance with theinvention may be Jkept substantially -so low that any resultantpressures will remain moderate.

The increase in 1 speed of reaction by theme oficadmium within the scopeof one embodiment of the invention permits shorter reaction periodsandlor l'ower :rea'ction temperatures for the *production of sebacicacid tor sebacic acid salts and thus more :efiicient, more :advantageousoperations as well :as a saving in wear of materials.

In the herein after set forth examples furnished by way of illustrationand not by way iOf limitation, the following procedural steps wereinvolved. The initial reaction mixes were heated in an autoclave ofstainless steel 316 and provided with a stirrer arrangement. Heating wascarried to the reaction temperature and was maintained for apredetermined period of time. When adding cadmium compounds a copperinsert was used which in the course of time became coated with a cadmiumlayer. "Pressure was released sometimes during the reaction, so that thepressure was not-higher than this one, given in the examples. Aftercompleted reaction and a certain dropping of temperature of the reactionmix, the pressure was completely released and the autoclave contentswere dissolved in water or diluted with water and the octanol and'octanone, if any, produced during the reaction were driven oif withsteam after the acidification of the solution with sulfuric acid to a pHof about 6. Sebacic acid remaining in solution after the separation ofthe precipitated fatty acids was obtained in readily fi-lterable form byfurther acidification of the hot solution and permitting the same tocool. The melting'point of the sebacic acid was 130-132 C.

Example I Starting materials: 339 g. castor oil, 300 g. soy fatty acid(JV=108), 205 g. NaOH,'205 g. water, 18g. CdO. Autoclave: Copper clad.Reaction: '2 hours at 300320 C., pressure not higher than 144 kg./cmYields:

172 g. sebacic acid=5l% of an castor oil=88% of theory. '70 g. octanol.340 g. fatty acids.

' By partial decomposition of the unsaturated soy fatty acids intosaturated fatty acids the idoine value of .the fatty acids after thereaction was 45. .By prolonged reaction time, the decompositioncompleted and the iodine value of the fatty acids lowered.

Example 11 Starting materials: 339 g. castor oil, 300 g. soy fatty acid,205 g. NaOH, 27 g. water, 18 g. CdO. Autoclave: Copper clad. Reaction:4% hours 250'300 C., pressure .not higher than 136 kg./cm Yields:

150 g. sebacic acid=44% of the castor oil:. 76% of theory. 48.5 g.octanol. 356 g. fatty acids.

Example 111 Starting materials: 339 g. castor oil, 300 g. of a mixtureof fatty alcoh ls from sperm oil, 160 g. NaOH, 27 g. water, 18 g. CdO.

Autoclave: Copper clad.

Reaction: 3 hours at.270-'300 C., pressure not higher than 168 kg./cm

Yields:

18 7 -'g. -sebacic acid=40.-2% -of-the*eastor -oil=70-% of theory.

21 g. octanol.

352 g. fatty acids small amounts of unsaponifiable, consistingtessentially of unreacted fatty alcohols.

-Example IV The additional "fatty acid .mix, .used in this example, wasproduced by air oxidation of a solid paratfin, obtained by catalytichydrogenation of carbon monoxide. The chaindength .of the .fatty acidswas .from 16 to 26 carbon atoms, the 1208.and.the .SV 220.

Starting materials: 600 ,g. fatty acids from castor oil, 2400 g.additional fatty acids, *600 g. of a technical caustic soda, containing.about 10% of water. No additional water, no additional cadmium.

Autoclave: Copper clad .with a cadmium lining, formed during foregoingreactions. p Reaction: .5 hours at 280-300 C., .Zpressure not higherthan 3.0 "kg/cm? p I p v Yields: 296 1g. tsebacica'cid=8 t% of theory.Theyie'lds .in octanol and .mono'basic *fatty 'acids were not de-'termined.

The sebacic acid referred toxhereinlis intended-'Ito'desig .nate nhe.acid typified :by 1&8 .octanedicarboxylic tacid. Fatty acids :as .used.herein :are intended atO designate organic acids within the broadconnotation of that term and substantially liquid at the operati'onaltemperature of sebacic acid formation within the scope of "thisinvention. The fatty acids within the broad scope of the inventioninclude as herein. above pointed out those of straight or branched chainconfigurations .tincluding *o'lefinic :acids and regardless of whetherof natural 'or synthetic origin. Within the preferred scope of theinvention the .so-called .fat acids thaviing melting points below .1 00"C. :fnrnish suitable additives in the practice of the invention. Theterm ffat racids here used is intended to designate :those acidsnormally occurring in animal or vegetable :fats, waxes :and oils, or,the otherwise, .inclnding synthetically produced, equivalents thereof.

1. In the method for the production of sebacic acid by the treatment ofthe alkali maps of castor oil and ricinoleic acid with caustic alkafisat increased tern .peratures, the improvement which comprises conductingsaid caustic alkali treatment in the presence of an additional alkalisoap of a fatty acid substantially :liquid at the said treatingtemperature and thereafter recovering sebacic acid from the reactionmix.

2. Improvement in accordance with claim 1 in which a fatty alcoholcorresponding to said fatty acid is added to the reaction mix to therebyproduce during said treatment the said ifatty acid alkali soap.

3. Improvement in accordance with claim 1 in which there .is added tothe reaction :mix an unsaturated fatty acid .free from. hydroxyl groupsto thereby obtain said fatty acid soap during said treatment.

4. Improvement in accordance with claim 1 in which :said treatment iscarried out in the presence of at least one member of the groupconsisting of cadmium and cadmium containing materials.

5. Improvement in accordance with claim 1 in which treatment is carriedout at a temperature of from substantially 200 C. to below thedecomposition temperature of the reactants and said sebacic acid and thesalts thereof.

6. Improvement in accordance with claim 5 in which said treatment iscarried out in the presence of at least :one :member of the groupconsisting of cadmium and cadmium containing materials.

7. Improvement in accordance with claim 6 in which said treatment iscarried out in the presence of water.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date [2,182.056 Bruson et a1 Dec; 5 1939 2.217.516 Houpt Oct. '8,1940 2.318.762 Davis et al. May ll, 1943 2.384.811 Chitwood Sept. 18,1945 2,580,931 Lane Ian-1, 1952

1. IN THE METHOD FOR THE PRODUCTION OF SEBACIC ACID BY THE TREATMENT OFTHE ALKALI SOAPS OF CASTOR OIL AND RICINOLEIC ACID WITH CAUSTIC ALKALISAT INCREASED TEMPERTURES, THE IMPROVEMENT WHICH COMPRISES CONDUCTINGSAID CAUSTIC ALKALI TREATMENT IN THE PRESENCE OF AN ADDITIONAL ALKLISOAP OF A FATTY ACID SUBSTANTIALLY LIQUID AT THE SAID TREATINGTEMPERATURE AND THEREAFTER RECOVERING SEBACIC ACID FROM THE REACTIONMIX.